Hitherto, a housing of a vacuum valve formed to have approximately uniform wall thickness by a squeezing process for one pipe material is heretofore known by, for example, Japanese Examined Patent Application Publication No. 3032708. The vacuum valve is provided with a valve seat formed into a flat surface shape by a squeezing process and a valve member for opening and closing the valve seat inside the housing having a cylindrical shape. An operating portion (cylinder portion) for opening and closing the valve member is attached to an upper end portion of the housing.
As described above, when the housing of the vacuum valve is formed by a drawing process for pipe material, the housing can be manufactured with simple and inexpensive manner. This is because there is no need to perform an expensive and complicated machine work. In addition, this is effective for a weight saving for the vacuum valve because the housing can be formed to have a thin wall thickness.
However, at the same time, the thin-walled housing causes an attaching operation for the operating portion to be difficult. As a matter of fact, in the heretofore known vacuum valve, an annular supporting member is attached to the upper end portion of the housing, while utilizing the wall thickness of the housing without modification, and the operating portion is attached onto the supporting member. Alternatively, an adaptor combined with the operating portion is directly attached onto the upper end portion of a cylinder. However, such a method, in which the operating portion is attached while utilizing the small wall thickness of the housing without modification, tends to not only result in small attaching strength, but also result in growing in size of the vacuum valve. This is because the supporting member overhangs to an outer periphery of the housing at large amount.